const defaultState={
    msg:'哈哈哈哈哈'
}
const reducer = (state=defaultState,action)=>{
    if(action.type === 'btn_change'){
        // state.msg = action.value
        // return state
        // 最好不要直接更改原来的state
        var newState = {...state}
        newState.msg = action.value
        return newState
    }
    return state
}
export default reducer